Such positive displacement pumps are used in modern-day motor vehicles, for example for conveying lubricating oil in the combustion engine or gear oil in the gearbox, and are known from practice. The areas of application mostly have different design points; however, these design points are achieved by means of corresponding operating stages of the pump stage and of the drive unit. The design points relate in particular to a small conveying quantity at high pressure or a large conveying quantity at low pressure, according to the operating state of the gearbox or of the combustion engine.
A positive displacement pump has become known from DE 36 14 819 C2, in which a supply is provided to a high-pressure circuit and a low-pressure circuit by means of a divided kidney-shaped pressure cavity. The pump stage also has two pump chambers separated by a center wall.